Shoe for swash-plate type compressor

ABSTRACT

A method of manufacturing a shoe including cutting a columnar raw material to a given length to provide a disc-shaped raw material, forming on one end face of the disc-shaped raw material a spherical sliding surface which is to be disposed in sliding contact with a spherical surface on a piston, and forming a thermal sprayed layer on the other end face of the disc-shaped raw material. The thermal sprayed layer serves as a flat plate-shaped sliding surface which is to be disposed in sliding contact with a swash plate. A shoe which is provided with the thermal sprayed layer exhibits an increased seizure resistance in comparison to a conventional shoe which is formed with a sintered layer, and can be manufactured inexpensively.

TECHNICAL FIELD

The present invention relates to a shoe and a method of manufacturingsame, and more particularly, to a shoe which is used in a swash platecompressor and a method of manufacturing same.

BACKGROUND OF THE INVENTION

A method of manufacturing a shoe which is used in a swash platecompressor known heretofore is as follows:

Specifically, in a first manufacturing method, a columnar raw materialof a given diameter is cut to a given length to provide a disc-shapedraw material, one end face of which is formed with a sintered layer,which is then formed into a sliding surface in the form of a flat platethat is to be disposed in sliding contact with a swash plate.Subsequently, the other end face of the disc-shaped raw material isformed with a spherical recess or a spherical sliding surface comprisedof a spherical recess, that is to be disposed in sliding contact with aspherical surface on a piston.

Alternatively, in a second manufacturing method, a steel plate ispreviously formed with a sintered layer on one of its surfaces, and theplate-shaped raw material is punched into a columnar configuration toprovide a columnar raw material. The surface which is provided with thesintered layer is formed into a sliding surface in the form of a flatplate that is to be disposed in sliding contact with a swash plate,while the other end face of the disc-shaped raw material is formed witha spherical recess or a spherical sliding surface comprised of aspherical recess that is to be disposed in sliding contact with aspherical surface on a piston.

The first manufacturing method has an advantage of good material yieldbecause the columnar raw material is cut to a given length to providethe disc-shaped raw material, but has a disadvantage in respect of costsrequired because the work is complicated because of the need ofproviding the disc-shaped raw material and then forming the sinteredlayer thereon.

On the other hand, according to the second manufacturing method, becauseone surface of the steel plate is formed with the sintered layer, thestep of forming the sintered layer is facilitated in comparison to thefirst manufacturing method, while the plate-shaped raw material which isformed with the sintered layer is punched into the columnarconfiguration to provide the columnar raw material, thus degrading thematerial yield to result in a disadvantage in respects of costsrequired.

In either manufacturing method, the use of the sintered layer resultedin a given limit being placed in improving the performance in respect ofseizure resistance.

DISCLOSURE OF THE INVENTION

In view of the foregoing, the present invention provides a shoe and amethod of manufacturing same which provide an excellent seizureresistance while allowing its manufacture in an inexpensive manner incomparison to the prior art.

Thus, the present invention relates to a shoe having a flat plate-shapedsliding surface which is adapted to be disposed in sliding contact witha swash plate and a spherical sliding surface which is adapted to bedisposed in sliding contact with a spherical surface on a piston;

characterized in that a thermal sprayed layer is formed on the flatplate-shaped sliding surface of the shoe, the surface of the thermalsprayed layer serving as a flat plate-shaped sliding surface.

The present invention also provides a method of manufacturing a shoewhich comprises a step of cutting a columnar raw material to a givenlength to provide a disc-shaped raw material, a step of forming on oneend face of the disc-shaped raw material a spherical sliding surfacewhich is adapted to be disposed in sliding contact with a sphericalsurface on a piston, and a step of forming a thermal sprayed layer onthe other end face of the disc-shaped raw material by a H.V.O.F. (HighVelocity Oxygen Fuel) spraying process, thus providing the thermalsprayed layer which serves as a flat plate-shaped sliding surface thatis adapted to be disposed in sliding contact with a swash plate.

With the manufacturing method mentioned above, the columnar raw materialis cut to a given length to provide the disc-shaped raw material, thusachieving a good material yield. In addition, the thermal sprayed layeris formed on the end face of the disc-shaped raw material. As comparedwith forming a sintered layer according to the prior art, the step offorming the thermal sprayed layer is facilitated, whereby the shoe canbe manufactured inexpensively.

A shoe with the thermal flame sprayed layer exhibits a greater seizureresistance than a shoe with a sintered layer, and allows a more reliableoperation of a swash plate compressor to be secured, in particular,under an underlubricated condition.

Where the H.V.O.F. spraying process is employed for the thermalspraying, a higher rate of thermal spraying produces a thermal sprayedlayer which is more dense and which exhibits a greater strength ofadhesion with the columnar raw material, whereby a highly excellentseizure resistance can be expected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a series of manufacturing steps showing oneembodiment of the present invention;

FIG. 2 is an enlarged cross section showing a completed shoe; and

FIG. 3 is a diagram of test results illustrating the seizure resistanceof the shoe according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A manufacturing method according to the present invention will bedescribed below with reference to an embodiment shown. As shown in FIG.1, a columnar raw material 1 having a diameter of 19 mm, which maycomprise S45C, for example, is initially cut to a given length L toprovide a disc-shaped raw material 2.

A conical opening 3 having an angle of 105° is then formed into one endface of the disc-shaped raw material 2, and a ball 4 having a diameterof 11 mm is pressed into the opening 3 to form a spherical recess 5 inan axially intermediate portion of the conical opening 3. The purpose ofthe spherical recess 5 is to allow a shoe to be ganged with a piston ofa swash plate compressor through a ball, not shown.

A H.V.O.F. spraying process is then applied to the other end face of thedisc-shaped raw material 2 or the end face thereof which is adapted toact as a sliding surface in the form of a flat plate that is to bedisposed in sliding contact with a swash plate, not shown, thus forminga thermal sprayed layer 6 thereon to a thickness of 0.4 mm. During thisprocess, the end face of the disc-shaped raw material 2 which is to bethermal sprayed is oriented upward for conducting the thermal spraying.

Upon removing a surplus portion 6 a of the flame sprayed layer 6 whichextends outside the outer peripheral surface of the disc-shaped rawmaterial 2, a through-opening 7 which measures 3 mm in diameter isformed in alignment with the axis of the disc-shaped raw material 2,thus communicating the spherical recess 5 with the thermal sprayed layer6 side through the through-opening 7. The through-opening 7 serves as anoil reservoir.

Additionally, a Cu plating layer 8 is then applied to a thickness of20-30 μm to the entire area of the disc-shaped raw material 2 and thethermal sprayed layer 6, whereupon the surface of the thermal sprayedlayer 6 inclusive of the plating layer 8 is removed to a thickness onthe order of 0.1 mm, thus providing its surface which acts as a slidingsurface 9 in the form of a flat plate that is to be disposed in slidingcontact with the swash plate. The Cu plating layer 8 is formed inconsideration of the sliding movement between the spherical recess 5 anda ball, not shown.

The ball 4 mentioned above is now again pressed into the sphericalrecess 5 to correct for any distortion caused by the thermal sprayingoperation, thus providing the surface of the spherical recess as aspherical sliding surface 10.

A chamfer 11 is then formed in a peripheral region from the thermalsprayed layer 6 to the columnar raw material 2, and a chamfer 12 is alsoformed around the inner peripheral surface of the through-opening 7which is located toward the flat plate-shaped sliding surface 9.

The end face of the columnar raw material 2 which faces away from theflat plate-shaped sliding surface 9 or the end face having the sphericalsurface is shaved off through a reduced thickness so that the axiallength of the columnar raw material 2 and the thermal sprayed layer 6becomes equal to a given length.

Subsequently, a large chamfer 13 having an angle of 30° is formed aroundthe outer periphery of the end face of the columnar raw material 2 whichhas the spherical surface, and the flat plate-shaped sliding surface 9is then subject to a lapping and a buffing sequentially to have athickness of the flat plate-shaped sliding surface 9 which is in a rangeof 0.15-0.25 mm, thus providing a completed product of shoe 14 which isshown to an enlarged scale in FIG. 2.

When the rapid gas flame spraying process is applied to the flatplate-shaped sliding surface side of the shoe 14 to form the thermalsprayed layer 6 thereon in this manner so that the surface of thethermal sprayed layer 6 serves as the flat plate-shaped sliding surface9, there can be obtained a shoe having a seizure resistance which isimproved over the prior art.

FIG. 3 shows results of a test which determined the seizure resistance.

The test comprises rotating a disc formed by an FCD hardened material,bringing a shoe into abutment under pressure against the surface of thedisc, and determining a load where a seizure occurs.

(Test Conditions)

Peripheral speed of shoe at point of contact: 15 m/s Load: 0.4 kN/10min, gradually increasing

Lubricant: ice machine oil.

The product according to the present invention has the flame sprayedlayer 6 applied to the raw material S45C to a thickness of 0.15-0.25 mmby the rapid gas flame spraying process, and the flame sprayed layer 6has components of remainder Cu-10 Sn-10Pb by weight percentage.

Control A is a shoe which is entirely formed of phosphor bronze(remainder Cu-6.5 Sn-0.2P).

Control B comprises S45C raw material on which a sintered layer isformed, the sintered layer having the same components as the product ofthe invention, namely, remainder Cu-10 Sn-10Pb.

Control C comprises a shoe which is entirely formed of T6 treatment ofremainder Al-17 Si-4.5 Cu-0.5 Fe-0.5 Mg-0.1 Mn.

Control D comprises a shoe which is entirely formed of T6 treatment ofremainder Al-17 Si-4 Cu-5 Fe-1.2 Mg-0.5 Mn.

As will be evident from test results shown in FIG. 3, the product of thepresent invention exhibits an excellent seizure resistance, and inparticular, demonstrates its superior effect over the control B in whichthe same components as in the product of the present invention aresintered together.

Components to form the flame sprayed layer 6 according to the presentinvention may be a Cu alloy comprising at least one or two or more ofadded components consisting of 40% or less of Pb, 30% or less of Sn,0.5% or less of P, 1.5% or less of Al, 10% or less of silver, 5% or lessof Si, 5% or less of Mn, 5% or less of Cr, 20% or less of Ni and 30% orless of Zn, all represented by weight percentage, and a remainder of Cu.

By using a Cu alloy having such components, a more excellent seizureresistance performance can be obtained.

In particular, when using a Cu alloy, it is desirable that a thermalsprayed layer be formed from a mixture of undissolved texture anddissolved texture of atomized powders of the Cu alloy. Thus, atomizedpowders are generally dissolved as they are pumped into a flame by agas, but part of the atomized powders can be left within the thermalsprayed layer by preventing the dissolution of part thereof during thethermal spraying operation as by expediting the cooling action. A moreexcellent seizure resistance performance can be obtained with a thermalsprayed layer which retains such texture.

To serve as the flame sprayed layer of the present invention, an Alalloy thermal sprayed layer comprising 12-60% by weight of Si and aremainder of Al substantially and in which particulate Si is dispersedin a matrix can be used. 0.1-30% of Sn may be contained in this flamesprayed layer and Sn particles may be dispersed in a matrix. Inaddition, at least one or more of added components consisting of 7% orless of Cu, 5% or less of Mg, 1.5% or less of Mn, 1.5% or less of Fe and8% or less of Ni may also be contained.

An excellent seizure resistance performance can be obtained with an Alalloy having such components.

As compared with the strength of adhesion of 150-200 Kg/cm² which isobtained between a plasma sprayed layer and a raw material, such astrength of adhesion obtained with the H.V.O.F. spraying process is ashigh as 450-500 Kg/cm². It is generally admitted that the greater thestrength of adhesion, the more the abrasion resistance is improved, andaccordingly, it is desirable to employ the H.V.O.F spraying process whenforming the thermal sprayed layer 6. However, any other spraying processmay be used to form the thermal sprayed layer 6.

If any spraying process is used, the surplus portion 6 a of the thermalsprayed layer 6 which projects outside the outer peripheral surface ofthe disc-shaped raw material 2 or any sprayed material which is sprayedon locations other than the disc-shaped raw material 2 can be recoveredfor reuse, which is an economical advantage.

In the described embodiment, the spherical sliding surface 10 which isconcave is formed and is arranged to be ganged with a piston through aball, but it should be understood that a convex spherical slidingcontact surface may be formed for direct ganged motion with the piston,as is well known in the art.

In the described embodiment, the spherical recess 5 is formed before thethermal sprayed layer 6 is formed, but it is possible to reverse thesequence of these steps.

INDUSTRIAL AVAILABILITY

As discussed above, the present invention brings forth an effect that ashoe having an increased seizure resistance can be manufacturedinexpensively in comparison to the formation of a sintered layer.

What is claimed is:
 1. A shoe having a flat plate-shaped sliding surfacedisposed for sliding contact with a swash plate and a spherical slidingsurface disposed for sliding contact with a spherical surface on apiston; wherein a thermal sprayed layer is formed on the flatplate-shaped sliding surface of the shoe, the surface of the thermalsprayed layer acting as a flat plate-shaped sliding surface, and thethermal sprayed layer comprises 12-60% by weight of Si and a remaindersubstantially of Al, with particulate Si being dispersed in a matrix. 2.A shoe according to claim 1, wherein the thermal sprayed layer comprises0.1-30% by weight of Sn, with Sn particles being dispersed in a matrix.3. A shoe according to claim 2, wherein the thermal sprayed layercomprises at least one or more added components consisting of 7% or lessof Cu, 5% or less of Mg, 1.5% or less of Mn, 1.5% or less of Fe and 8%or less of Ni, all represented by weight percentage.
 4. A shoe for usein a swash plate-type compressor having a piston and a swash plate forcausing reciprocating movement of the piston, said shoe comprising: afirst spherical surface disposed for sliding contact with the piston;and a second planar surface facing in an opposite direction from saidfirst surface and disposed for sliding contact with the swash plate,said second surface including a thermally sprayed layer thereoncomprising an Al alloy to minimize seizure of said piston and said shoe;said thermally sprayed layer comprising 12-60% by weight of Si and aremainder substantially of Al, with particulate Si being dispersed in amatrix.
 5. The shoe of claim 4 wherein said first surface comprises aspherically concave recess for sliding contact with a spherically convexportion of the piston.
 6. The shoe of claim 5 including an oil reservoirdefined by a through-opening extending between said first and secondsurfaces, a first chamfered portion formed along an outer periphery ofsaid second surface, and a second chamfered portion formed along anouter periphery of said first surface.
 7. The shoe of claim 4 furthercomprising a base material of steel which defines said first and secondsurfaces thereon, and said thermally sprayed layer defining an outermostsurface of said shoe for sliding contact with the swash plate.